Pixel structure for liquid crystal display

ABSTRACT

The present invention builds a metal electrode that is controlled by the common electrode in each pixel cell. During operation, a voltage is first applied to this metal electrode to transform the liquid crystal molecule over this metal electrode from the splay state into the bend state. Next, a voltage is applied to the pixel electrode to transform the liquid crystal molecule in the whole pixel region from the splay state into the bend state. Two different voltage field also can be respectively applied to the common electrode and the pixel electrode.

This application is a continuation application of Ser. No. 10/936,752,filed on Sep. 9, 2004, which is a continuation-in-part of applicationSer. No. 10/672,906, filed on Sep. 25, 2003.

FIELD OF THE INVENTION

The present invention relates to a pixel structure for a liquid crystaldisplay and more particularly to a high speed response pixel structurefor a liquid crystal display.

BACKGROUND OF THE INVENTION

Twisted nematic (TN) cells, which at present are widely used in TFTcolor liquid crystal display devices (TFT/LCDs), have a small view-fieldangle. This results in a decrease in contrast and image inversion whenan LCD panel surface is viewed from an oblique direction. Variousmethods have been proposed to solve this problem, i.e., to realize awide view-field angle. Among these methods is an orientation divisionmethod in which each pixel of an LCD is divided into two parts andorientation is affected in different directions in the two parts.

However, these methods require cumbersome manufacturing steps. Forexample, in the case of the orientation division method, two rubbingsteps are required. These steps include the further steps of coating,baking, patterning, developing and removing photoresist.

In recent years, studies on an OCB cell that is to be used as a liquidcrystal cell instead of a TN cell have been made. If the OCB celltechnique is used, it becomes possible to obtain a wide view-field anglemore easily than with the orientation division method as well as ahigh-speed response characteristic that is one order faster than withconventional TN cells.

FIG. 1 is a perspective view illustrating the structure of an OCB cell.A liquid crystal material that exhibits splay orientation 104 is sealedbetween two (top and bottom) glass substrates 100 and 102. Polarizingplates 106 and 108 are disposed outside the two respective glasssubstrates 100 and 102. When a voltage is applied to the glasssubstrates 100 and 102, the liquid crystal material is transformed fromsplay orientation 104 to bend orientation 110 as shown in FIG. 1B. In abend orientation 110 cell, since top and bottom liquid crystal moleculesare always oriented symmetrically, the view-field-angle dependence issymmetrical around the AA′ line. An optically compensated bend (OCB)mode LCDs compensates for the birefringence of liquid crystal moleculesso as to obtain the uniform viewing angle characteristic at alldirections.

An OCB cell is in a splay orientation state when no bias voltage isapplied thereto, and exhibits a bend orientation state when a given highvoltage is applied thereto. To allow an OCB cell to operate as a liquidcrystal display device, the cell must be transformed from a splayorientation to bend orientation at the start of operation. This processrequires a restart time, which reduces the response speed.

FIG. 2A shows a pixel structure plan diagram of a thin-film transistorLCD. The gate electrode 306 a of the switch transistor 306 is connectedto the scan line 302. The drain electrode 306 b of the switch transistor306 is connected to the pixel electrode 308 and the source electrode 306c is connected to the video data line 304. A common line 310 is used asthe common electrode of the pixel electrode 308. The switch transistor306 is usually a thin-film transistor (TFT) that is deposited on atransparent substrate such as glass. By scanning the scan lines 302 andin accordance with the scan signals, all of the switch transistors 306in a given scan line 302 are turned on. At the same time, video signalsare provided in the video data lines synchronously with the selectedscan line 302.

FIG. 2B is a cross-sectional view along the BB′ line in FIG. 2A. Aliquid crystal material 326 is sealed between two (top and bottom) glasssubstrates 320 and 322. A conductor electrode 324 is located on the topglass substrate 320. Referring to FIG. 2A and FIG. 2B, typically, theliquid crystal molecule 328 over the pixel electrode 308 is in splaystate and the liquid crystal molecule 326 over the other region is inbend state. Then, a high voltage is applied between the conductorelectrode 324 and the pixel electrode 308 for a given period at thestart of operation of a liquid crystal display device using the OCBcell. At this time, the liquid crystal molecule 326 in bend orientationchange the orientation state of the liquid crystal molecule 328 over thepixel electrode 308 from splay orientation to bend orientation. However,a part of the liquid crystal molecule 328 over the pixel electrode 308may be unsuccessfully transformed and remain in bend orientation, whichreduces the display quality of the LCD. In addition, the two orientationstates required in this method increase the manufacturing cost.Moreover, it is difficult to maintain the high angle of inclination of abend orientation state liquid crystal molecule. Although this allows theliquid crystal display device to have a desired wide view-field anglecharacteristic, the image quality required for it cannot be obtainedeasily. Further, the above measure is not practical.

FIG. 2C shows another orientation state in accordance with theconventional method. The liquid crystal molecule 330 in the whole pixelis in splay state. In accordance with this method, a high voltage isapplied between the conductor electrode 324 and the pixel electrode 308for a given period at the start of operation of a liquid crystal displaydevice using the OCB cell to transform the liquid crystal molecule 330from splay state into the bend state. This fixed start time usuallytakes more than several tens of seconds. The liquid crystal molecule 330returns to splay state when the LCDs is turned off. However, part of theliquid crystal molecule 330, such as the liquid crystal molecule betweenthe video data line 304 and the pixel electrode 308, is applied to thehigh voltage in this mode, which causes two liquid crystal moleculestates when the LCDs is turned on. Yet another problem is that even ifthe liquid crystal molecule 330 is transformed from splay orientation tobend orientation at the start of operation, the OCB cell may return tosplay orientation during operation. The LCD must be restarted fordisplay to return to normal.

On the other hand, recent battery-driven systems such as notebook-typepersonal computers equipped with a TFT color liquid crystal displaydevice are increasingly required to be of a power-saving type. Toconserve power, such a liquid crystal display device has a driving modestop function to turn off a display thereof. Once the LCD is turned off,an OCB cell returns to splay orientation from bend orientation. A periodof time is needed to restore the bend orientation state; thus thedisplay cannot be turned on instantaneously.

SUMMARY OF THE INVENTION

In accordance with the foregoing description, the typical liquid crystaldisplay using OCB cell requires transformation of the liquid crystalmolecule orientation state from splay orientation to bend orientationduring operation, which involves two liquid crystal molecule orientationstates. There are two typical transformation methods. In one method theliquid crystal molecule over the pixel electrode is first in a splaystate while the liquid crystal molecule over the other region is in abend state. Then, a high voltage is applied between the conductorelectrode and the pixel electrode to transform the liquid crystalmolecule over the pixel electrode from splay state into the bend state.However, this method requires two different orientation states, splaystate and bend state, and the manufacturing cost is increased. Inanother method, the liquid crystal molecule in the whole pixel in asplay state. Although an LCD employing this method is convenient tomanufacture, this method requires a given period at the start ofoperation of a liquid crystal display device to transform the liquidcrystal molecule from splay state into the bend state. In other words,this method does not provide an instantaneous response. Moreover, partof the liquid crystal molecule does not accept high voltage, whichaffects the display quality.

Therefore, it is the main object of the present invention to provide apixel structure capable of obtaining a wide viewing angle as well asimproving picture quality.

Another purpose of the present invention is to provide a pixel structureonly using an unique orientation state in the whole cell and for which agiven period at the start of operation of a liquid crystal displaydevice is not necessary.

Yet another purpose of the present invention is to provide a drivingmethod of a liquid crystal display device, which method allows an OCBcell to transform from a splay orientation to a bend orientation statein a short period.

A further purpose of the present invention is to provide a liquidcrystal display that can be manufactured in a simple and relativelyinexpensive manufacturing method.

In accordance with the present invention, a metal electrode is built inthe pixel region. The metal electrode is controlled by the commonelectrode. The liquid crystal molecule in the whole pixel region is in asplay state. A voltage is applied to the metal electrode to transformthe liquid crystal molecule over the metal electrode from splay stateinto the bend state during during operation. Then, a voltage is appliedto the pixel electrode. At this time, the liquid crystal molecule in thebend state transforms the liquid crystal molecule over the pixelelectrode from the splay state into the bend state. Therefore, theliquid crystal molecule in the whole pixel region exhibits the bendstate.

The metal electrode can be positioned in the center of the pixelelectrode or around the pixel electrode in accordance with the presentinvention. A complicated manufacturing process can be avoided becausethe present invention does not require two orientation states in aliquid crystal cell. Moreover, a given period for transforming theliquid crystal molecule from the splay state into the bend state at thestart of LCDs operation is not necessary. Therefore, the LCDs using thepixel structure of the present invention exhibits a high speed responseas well as a high display quality.

On the other hand, the present invention also provides a drive circuitfor driving the metal electrode. The drive circuit includes an inverterto invert the field frame inputted to the source/drain electrode of atransistor. The inverted field frame is used to control the commonelectrode. On the other hand, this transistor is controlled by a scansignal. Therefore, this transistor operation is synchronized with theswitch transistor operation. In other words, if a voltage is applied insequence to the metal electrode and the pixel electrode, the drivecircuit first turns on the transistor and then inverts the field frame.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated and better understood byreferencing the following detailed description, when taken inconjunction with the accompanying drawings, wherein:

FIG. 1A illustrates a schematic configuration diagram of a liquidcrystal display using OCB mode, wherein the liquid crystal molecule isin the splay state;

FIG. 1B illustrates a schematic configuration diagram of a liquidcrystal display using OCB mode, wherein the liquid crystal molecule isin the bend state;

FIG. 2A illustrates a pixel structure plan diagram of a thin-filmtransistor LCD;

FIG. 2B illustrates a cross-sectional view along the BB′ line of FIG.2A, in which some of the liquid crystal molecules are in the splay stateand some are in the bend state;

FIG. 2C illustrates a cross-sectional view along the BB′ line of FIG.2A, wherein all of the liquid crystal molecules are in the splay state;

FIG. 3A illustrates a top view of the pixel region in accordance withthe first embodiment of the present invention;

FIG. 3B illustrates a cross-sectional view from the AA′ line of FIG. 3A,wherein all of the liquid crystal molecules are in the splay state;

FIG. 3C illustrates a cross-sectional view from the AA′ line of FIG. 3A,in which some of the liquid crystal molecules are transformed into thebend state;

FIG. 4A illustrates a top view of the pixel region in accordance withthe second embodiment of the present invention;

FIG. 4B illustrates a cross-sectional view along the AA′ line of FIG.4A, in which all of the liquid crystal molecules are in the splay state;

FIG. 4C illustrates a cross-sectional view along the AA′ line of FIG.4A, in which some of the liquid crystal molecules are transformed intothe bend state;

FIG. 5A illustrates a top view of the pixel region in accordance withthe third embodiment of the present invention;

FIG. 5B illustrates a cross-sectional view from the AA′ line of FIG. 5A,in which all of the liquid crystal molecule are in the splay state;

FIG. 5C illustrates a cross-sectional view from the AA′ line of FIG. 5A,in which parts of the liquid crystal molecules are transformed into thebend state;

FIG. 6A illustrates a top view of the pixel region in accordance withthe fourth embodiment of the present invention;

FIG. 6B illustrates a cross-sectional view from the AA′ line of FIG. 6A,in which all of the liquid crystal molecules are in the splay state;

FIG. 6C illustrates a cross-sectional view from the AA′ line of FIG. 6A,in which some of the liquid crystal molecules are transformed into thebend state;

FIG. 7A illustrates a top view of a pixel region that the commonelectrode line with connected metal line and the video data line arearranged in the same layer;

FIG. 7B illustrates a cross-sectional view from the AA′ line of FIG. 7A,in which some of the liquid crystal molecules are transformed into thebend state;

FIG. 8A illustrates a waveform from negative to positive of drive timingin accordance with the first embodiment;

FIG. 8B illustrates a waveform from positive to negative of drive timingin accordance with the first embodiment;

FIG. 9A illustrates a waveform from negative to positive of drive timingin accordance with the second embodiment;

FIG. 9B illustrates a waveform from positive to negative of drive timingin accordance with the second embodiment;

FIG. 10A illustrates a waveform from negative to positive of drivetiming in accordance with the third embodiment;

FIG. 10B illustrates a waveform from positive to negative of drivetiming in accordance with the third embodiment;

FIG. 11 illustrates a top view of using the pixel electrode structure ofthe present invention to a TFT-LCDs;

FIG. 12A illustrates a drive circuit schematic diagram for generating adrive voltage;

FIG. 12B illustrates a detailed diagram of a drive circuit forgenerating a drive voltage;

FIG. 13A illustrates a schematic diagram of the liquid crystal moleculesaligned in the direction perpendicular to the metal electrode;

FIG. 13B illustrates a schematic diagram of the liquid crystal moleculesaffected by a crosswise electrical field;

FIG. 14A illustrates a schematic diagram of the liquid crystal moleculesaligned in the direction parallel to the metal electrode;

FIG. 14B illustrates a schematic diagram of the liquid crystal moleculesaffected by a crosswise electrical field;

FIG. 15A illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe first embodiment of the present invention;

FIG. 15B illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe second embodiment of the present invention;

FIG. 15C illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe third embodiment of the present invention;

FIG. 15D illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe fourth embodiment of the present invention;

FIG. 15E illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe fifth embodiment of the present invention;

FIG. 15F illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe sixth embodiment of the present invention;

FIG. 15G illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe seventh embodiment of the present invention;

FIG. 15H illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe eighth embodiment of the present invention;

FIG. 16A illustrates a schematic diagram of a pixel structure appearancechange of FIG. 5A cooperating with this alignment method according tothe first embodiment of the present invention;

FIG. 16B illustrates a schematic diagram of a pixel structure appearancechange of FIG. 5A cooperating with this alignment method according tothe second embodiment of the present invention;

FIG. 16C illustrates a schematic diagram of a pixel structure appearancechange of FIG. 5A cooperating with this alignment method according tothe third embodiment of the present invention;

FIG. 17A illustrates a top view of holes located in a pixel electrode toexpose a metal electrode, in which no voltage is applied to the metalelectrode;

FIG. 17B illustrates a top view of holes located in a pixel electrode toexpose a metal electrode, in which a voltage is applied to the metalelectrode;

FIG. 18A illustrates a top view of a metal electrode with a sawtoothappearance, in which no voltage is applied to the metal electrode;

FIG. 18B illustrates a top view of a metal electrode with a sawtoothappearance, in which a voltage is applied to the metal electrode;

FIG. 19A illustrates a top view of a trench formed in a pixel electrodeto expose a common electrode, in which no voltage is applied to thecommon electrode;

FIG. 19B illustrates a top view of a trench formed in a pixel electrodeto expose a common electrode, in which a voltage is applied to thecommon electrode;

FIG. 20A illustrates a top view of a metal electrode extended out of thepixel electrode, in which no voltage is applied to the metal electrode;and

FIG. 20A illustrates a top view of a metal electrode extended out of thepixel electrode, in which a voltage is applied to the metal electrode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Without limiting the spirit and scope of the present invention, thecircuit structure proposed in the present invention is illustrated withone preferred embodiment. One with ordinary skill in the art, uponacknowledging the embodiment, can apply the pixel electrode structureusing the OCB mode and the operation method of the present invention tovarious liquid crystal displays. In accordance with the pixel structure,a complicated manufacturing process can be avoided because the pixelregion does not require two orientation states in a liquid crystal cell.Moreover, the present invention does not require a given period fortransforming the liquid crystal molecule from the splay state into thebend state at the start of LCD operation. Therefore, LCDs using thepixel structure of the present invention have a high speed response aswell as a high display quality. The application of the present inventionis not limited by the preferred embodiments described in the following.

In accordance with the present invention, a metal electrode is built inthe pixel region. The metal electrode is controlled by the commonelectrode. The liquid crystal molecules in the entire pixel region arein the splay state. A voltage is applied to the metal electrode totransform the liquid crystal molecule over the metal electrode from thesplay state into the bend state during operation. Then, a voltage isapplied to the pixel electrode. At this time, the liquid crystalmolecules in the bend state transform the liquid crystal molecule overthe pixel electrode from the splay state into the bend state. Therefore,the liquid crystal molecule in the whole pixel region exhibit the bendstate.

The First Embodiment

FIG. 3A shows a top view of the pixel region in accordance with thefirst embodiment of the present invention. The silicon island 506 a ofthe switch transistor 506 is connected to the scan line 502. When theswitch transistor 506 is selected, a scan signal is sent via the scanline 502 to turn the switch transistor 506 on. The video signal in thevideo data line 504 is transferred to the pixel electrode 508 throughthe switch transistor 506. The drain electrode 506 b of the switchtransistor 506 is connected to the pixel electrode 508. The sourceelectrode 506 c of the switch transistor 506 is connected to the videodata line 504. A common electrode line 510 is used as the commonelectrode of the pixel electrode 508. An “S”-type metal electrode 512 isbuilt around the pixel region. The metal electrode 512 is controlled bythe common electrode line 510.

Typically, the source electrode 506 c and the drain electrode 506 b ofthe switch transistor 506 can receive video data from the video dataline 504. Therefore, by scanning the scan lines 502 and in accordancewith the scan signals, the switch transistors 506 in a given scan line502 are turned on. At the same time, video signals in the video dataline 504 are transferred to the pixel electrode 508 through the switchtransistor 506 to show a picture on the liquid crystal display.

FIG. 3B shows a cross-sectional view along line AA′ of FIG. 3A, in whichall of the liquid crystal molecule are in the splay state. A lowersubstrate 514 and an upper substrate 516 are opposite each other with aspecific distance therebetween. The lower substrate 514 and the uppersubstrate 516 are preferably made of a transparent insulator. A liquidcrystal layer 518 having a plurality of liquid crystal molecules issandwiched between the lower substrate 514 and the upper substrate 516,in which the plurality of liquid crystal molecules is in the splaystate. The video data line 504 and the metal line 512 are sequentiallyformed over the lower substrate 514. An isolation layer 530 is locatedbetween the video data line 504 and the metal line 512. A pixelelectrode 508 is formed on the inner surface of the lower substrate 514.Another isolation layer 532 is located between the video data line 504and the pixel electrode 508. A conductor electrode 520 is formed on aninner surface of the upper substrate 516. Both the pixel electrode 508and the conductor electrode 520 are formed from a transparent conductor,and preferably, for example, an ITO material. Further, alignment layers(not shown in figure) are formed on an inner surface of the lowersubstrate 514 whereon the pixel electrode 508 is disposed and the uppersubstrate 516 whereon the conductor electrode 520 is disposed. Herein,the alignment layers have a pre-tilt angle of about 5 degrees in thesplay state.

A voltage is applied to the metal electrode 512 to transform the liquidcrystal molecule over the metal electrode 512 from the splay state intothe bend state during operation as shown in FIG. 3C. FIG. 3C shows across-sectional view along line AA′ of FIG. 3A, in which parts of theliquid crystal molecule are transformed into the bend state. Inaccordance with the first embodiment, a voltage is applied between thecommon electrode 510 and the conductor electrode 520 located on theupper substrate 516. Therefore, a voltage difference also exists betweenthe metal electrode 512 controlled by the common electrode 510 and theconductor electrode 520. Therefore, the liquid crystal molecule betweenthe metal electrode and the upper substrate 516 is transformed fromsplay state into bend state due to the voltage difference.

Further reference is made to FIG. 3C. The pixel electrode 508 is dividedinto two parts, 508 a and 508 b. A liquid crystal molecule 518 a in bendstate is used to divide the two parts 508 a and 508 b. It is noted thatthis liquid crystal molecule 518 a has an isolating function. Thevoltage difference between the metal electrode 512 and the conductorelectrode 520 still exists after the voltage difference between thepixel electrode and the conductor electrode 520 is created. In otherwords, this still-existing voltage difference ensures that the liquidcrystal molecules 518 a remain in the bend state. Therefore, the liquidcrystal molecules 518 a isolate influence from outside of the pixelelectrode in which the liquid crystal molecule is in a splay state. Whenthe liquid crystal display is turned off, the voltage applied to thecommon electrode 510 is removed. At this time, the liquid crystalmolecule between the common electrode 510 and the metal electrode 512 istransformed from the bend state into the splay state.

Reference is made to FIG. 3A again. During operation, the liquid crystalmolecule between the common electrode 510 and the metal electrode 512 isfirst transformed from the original splay state into the bend statebefore a voltage is applied to pixel electrode 508. Next, by scanningthe scan lines 502 and in accordance with the scan signals, the switchtransistor 506 in a given scan line 502 is turned on. At the same time,video signals in the video data line 504 are transferred to the pixelelectrode 508 through the switch transistor 506. In other words, avoltage difference is created between the pixel electrode 508 and theconductor electrode 520 in the upper substrate 516. At this time, theliquid crystal molecule in the pixel region are transformed from thesplay state into the bend state. Therefore, the liquid crystal moleculesin the whole liquid crystal region are in the bend state. On the otherhand, part of the metal electrode 512 may overlap with the pixelelectrode 508. The overlapping part then functions as a capacitor, whichraises the response velocity of the pixel electrode.

The Second Embodiment

FIG. 4A shows a top view of the pixel region in accordance with thesecond embodiment of the present invention. The silicon island 706 a ofthe switch transistor 706 is connected to the scan line 702. When theswitch transistor 706 is selected, the scan signal in the scan line 702turns on the switch transistor 706. The video signal in the video dataline 704 is transferred to the pixel electrode 708 through the switchtransistor 706. The drain electrode 706 b of the switch transistor 706is connected to the pixel electrode 708. The source electrode 706 c ofthe switch transistor 706 is connected to the video data line 704. Acommon electrode line 710 is used as the common electrode of the pixelelectrode 708. A metal electrode 712 is built around the pixel region.The metal electrode 712 is controlled by the common electrode line 710.

FIG. 4B shows a cross-sectional view along line AA′ of FIG. 4A. A lowersubstrate 714 and an upper substrate 716 are opposite each other with aspecific distance therebetween. The lower substrate 714 and the uppersubstrate 716 are preferably made of a transparent insulator. A liquidcrystal layer 718 having a plurality of liquid crystal molecules issandwiched between the lower substrate 714 and the upper substrate 716,in which the plurality of liquid crystal molecules is in the splaystate. The video data line 704 and the metal line 712 are sequentiallyformed over the lower substrate 714. An isolation layer 730 is locatedbetween the video data line 704 and the metal line 712. A pixelelectrode 708 is formed on the inner surface of the lower substrate 714.Another isolation layer 732 is located between the video data line 704and the pixel electrode 708. A conductor electrode 720 is formed on aninner surface of the upper substrate 716. Both the pixel electrode 708and the conductor electrode 720 are formed from a transparent conductor,and preferably, for example, an ITO material. Further, alignment layers(not shown in figure) are formed on an inner surface of the lowersubstrate 714 whereon the pixel electrode 708 is disposed and the uppersubstrate 716 whereon the conductor electrode 720 is disposed. Herein,the alignment layers have a pre-tilt angle of about 5 degrees in thesplay state.

A voltage is applied to the metal electrode 712 to transform the liquidcrystal molecule 718 a over the metal electrode 712 from the splay stateinto the bend state during operation as shown in FIG. 4C. FIG. 4C showsa cross-sectional view along line AA′ of FIG. 4A in accordance with thesecond embodiment, in which parts of the liquid crystal molecule aretransformed into the bend state. In accordance with the secondembodiment, a voltage is applied between the common electrode 710 andthe conductor electrode 720 located on the upper substrate 716.Therefore, a voltage difference also exists between the metal electrode712 controlled by the common electrode 710 and the conductor electrode720. Therefore, the liquid crystal molecule between the metal electrode712 and the upper substrate 716 is transformed from the splay state intothe bend state due to the voltage difference as shown in FIG. 4C.

Again referring to FIG. 4C, a liquid crystal molecule 718 a, which is inbend state, is used to isolate the pixel electrode 708. The voltagedifference between the metal electrode 712 and the conductor electrode720 still exists after the voltage difference between the pixelelectrode 708 and the conductor electrode 720 is built. In other words,this still-existent voltage difference ensures that the liquid crystalmolecules 718 a maintain the bend state. Therefore, the liquid crystalmolecule 718 a isolates the pixel electrode 708 from the influenceoutside of the pixel electrode 708 in which the liquid crystal moleculeis in a splay state. When the liquid crystal display is turned off, thevoltage applied to the common electrode 710 is removed. At this time,the liquid crystal molecule between the common electrode 710 and themetal electrode 712 can be transformed from the bend state into thesplay state.

During operation, the liquid crystal molecule between the commonelectrode 710 and the metal electrode 712 is first transformed from theoriginal splay state into the bend state before a voltage is applied topixel electrode 708. Next, by scanning the scan lines 702 and inaccordance with the scan signals, the switch transistor 706 in a givenscan line 702 is turned on. At the same time, video signals in the videodata line 704 are transferred to the pixel electrode 708 through theswitch transistor 706. In other words, a voltage difference is createdbetween the pixel electrode 708 and the conductor electrode 720 in theupper substrate 716. At this time, the liquid crystal molecule in thepixel region can be transformed from the splay state into the bendstate. Therefore, the liquid crystal molecules in the whole liquidcrystal region are in the bend state now. On the other hand, part of themetal electrode 712 may overlap with the pixel electrode 708. Theoverlapping part functions as a capacitor, which raises the responsevelocity of the pixel electrode.

The Third Embodiment

FIG. 5A shows a top view of the pixel region in accordance with thethird embodiment of the present invention. The silicon island 806 a ofthe switch transistor 806 is connected to the scan line 802. The drainelectrode 806 b of the switch transistor 806 is connected to the pixelelectrode 808. The source electrode 806 c of the switch transistor 806is connected to the video data line 804. A common electrode line 810 isused as the common electrode of the pixel electrode 808. In accordancewith the third embodiment, the metal electrode 812 and the commonelectrode 810 are in the shape of an “H”. The metal electrode 812 iscontrolled by the common electrode line 810.

FIG. 5B shows a cross-sectional view along line AA′ of FIG. 5A. A lowersubstrate 814 and an upper substrate 816 are opposite each other with aspecific distance therebetween. The lower substrate 814 and the uppersubstrate 816 are preferably made of a transparent insulator. A liquidcrystal layer 818 having a plurality of liquid crystal molecules issandwiched between the lower substrate 814 and the upper substrate 816,in which the plurality of liquid crystal molecules is in the splaystate. The video data line 804 and the metal line 812 are sequentiallyformed over the lower substrate 814. An isolation layer 830 is locatedbetween the video data line 804 and the metal line 812. A pixelelectrode 808 is formed on the inner surface of the lower substrate 814.Another isolation layer 832 is located between the video data line 804and the pixel electrode 808. A conductor electrode 820 is formed on aninner surface of the upper substrate 816. Both the pixel electrode 808and the conductor electrode 820 are formed from a transparent conductor,and preferably, for example, an ITO material. Further, alignment layers(not shown in figure) are formed on an inner surface of the lowersubstrate 814 whereon the pixel electrode 31 is disposed and the uppersubstrate 816 whereon the conductor electrode 820 is disposed. Herein,the alignment layers have a pre-tilt angle of about 5 degrees in thesplay state. During operation, a voltage is applied to the metalelectrode 812 to transform the liquid crystal molecule 818 a over themetal electrode 812 from the splay state into the bend state as shown inFIG. 5C.

Referring to FIG. 5C again, a liquid crystal molecule 818 a, which is inthe bend state, is used to isolate the pixel electrode 808. In otherwords, the voltage difference between the metal electrode 812 and theconductor electrode 820 still exists after the voltage differencebetween the pixel electrode 808 and the conductor electrode 820 iscreated. In other words, this still-existent voltage difference ensuresthat the liquid crystal molecule 818 a maintains the bend state.Therefore, the liquid crystal molecule 818 a isolates the pixelelectrode 808 from influence from outside of the pixel electrode 808 inwhich the liquid crystal molecules are in a splay state. When the liquidcrystal display is turned off, the voltage applied to the commonelectrode 810 is removed. At this time, the liquid crystal moleculebetween the common electrode 810 and the metal electrode 812 istransformed from the bend state into the splay state.

During operation, the liquid crystal molecule between the commonelectrode 810 and the metal electrode 812 is first transformed from theoriginal splay state into the bend state before a voltage is applied topixel electrode 808. Next, by scanning the scan lines 802 and inaccordance with the scan signals, the switch transistor 806 in a givenscan line 802 is turned on. At the same time, video signals in the videodata line 804 are transferred to the pixel electrode 808 through theswitch transistor 806. In other words, a voltage difference is builtbetween the pixel electrode 808 and the conductor electrode 820 in theupper substrate 816. At this time, the liquid crystal molecule in thepixel region can be transformed from the splay state into the bendstate. Therefore, the liquid crystal molecule in the whole liquidcrystal region is now in the bend state. On the other hand, part of themetal electrode 812 overlaps the pixel electrode 808. The overlappingpart functions as a capacitor, which can raise the response velocity ofthe pixel electrode.

The Fourth Embodiment

FIG. 6A shows a top view of the pixel region in accordance with thefourth embodiment of the present invention. The silicon island 906 a ofthe switch transistor 906 is connected to the scan line 902. The drainelectrode 906 b of the switch transistor 906 is connected to the pixelelectrode 908. The source electrode 906 c of the switch transistor 906is connected to the video data line 904. A common electrode line 910 isused as the common electrode of the pixel electrode 909. In accordancewith the fourth embodiment, the metal electrode 912 and the commonelectrode 910 are in the shape of a cross. The metal electrode 912 iscontrolled by the common electrode line 910.

FIG. 6B shows a cross-sectional view along line AA′ of FIG. 5A. A lowersubstrate 914 and an upper substrate 916 are opposite each other with aspecific distance therebetween. The lower substrate 914 and the uppersubstrate 916 are preferably made of a transparent insulator. A liquidcrystal layer 918 having a plurality of liquid crystal molecules issandwiched between the lower substrate 914 and the upper substrate 916,wherein the plurality of liquid crystal molecules is in the splay state.The video data line 904 and the metal line 912 are sequentially formedover the lower substrate 914. An isolation layer 930 is located betweenthe video data line 904 and the metal line 912. A pixel electrode 908 isformed on the inner surface of the lower substrate 914. Anotherisolation layer 932 is located between the video data line 904 and thepixel electrode 908. A conductor electrode 920 is formed on an innersurface of the upper substrate 916. Both the pixel electrode 908 and theconductor electrode 920 are formed from a transparent conductor, andpreferably, for example, an ITO material. Further, alignment layers (notshown in figure) are formed on an inner surface of the lower substrate914 whereon the pixel electrode 31 is disposed and the upper substrate916 whereon the conductor electrode 920 is disposed. Herein, thealignment layers have a pre-tilt angle of about 5 degrees in the splaystate.

Referring to FIG. 5C again, a liquid crystal molecule 918 a, which is inthe bend state, is used to isolate the pixel electrode 908. In otherwords, the voltage difference between the metal electrode 912 and theconductor electrode 920 still exists after the voltage differencebetween the pixel electrode 908 and the conductor electrode 920 iscreated. This still-existent voltage difference ensures that the liquidcrystal molecule 918 a maintains the bend state. Therefore, the liquidcrystal molecule 918 a isolates pixel electrode 908 from the influencethe outside of the pixel electrode 908 in which the liquid crystalmolecule is in a splay state. When the liquid crystal display is turnedoff, the voltage applied to the common electrode 910 is removed. At thistime, the liquid crystal molecule between the common electrode 910 andthe metal electrode 912 is transformed from the bend state into thesplay state.

During operation, the liquid crystal molecule between the commonelectrode 910 and the metal electrode 912 is first transformed from theoriginal splay state into the bend state before a voltage is applied topixel electrode 909. Next, by scanning the scan lines 902 and inaccordance with the scan signals, the switch transistor 906 in a givenscan line 902 is turned on. At the same time, video signals in the videodata line 904 are transferred to the pixel electrode 908 through theswitch transistor 906. In other words, a voltage difference is createdbetween the pixel electrode 908 and the conductor electrode 920 in theupper substrate 916. At this time, the liquid crystal molecules in thepixel region are transformed from the splay state into the bend state.Therefore, the liquid crystal molecules in the whole liquid crystalregion are now in the bend state. On the other hand, part of the metalelectrode 912 overlaps with the pixel electrode 908. The overlappingpart functions as a capacitor, which can raise the response velocity ofthe pixel electrode.

It is noted that the common electrode line with the connected metalelectrode line and the video data line are located on different layersaccording to the foregoing four embodiments. However, the commonelectrode line with the connected metal electrode line and the videodata line can be located on the same layer in another embodiments. Forexample, FIG. 7A and FIG. 7B illustrate the structure of the commonelectrode line with the connected metal electrode line and the videodata line, described in the first embodiment, are located on the samelayer.

In FIG. 7A, the silicon island 506 a of the switch transistor 506 isconnected to the scan line 502. When the switch transistor 506 isselected, a scan signal is sent via the scan line 502 to turn the switchtransistor 506 on. The video signal in the video data line 504 istransferred to the pixel electrode 508 through the switch transistor506. The drain electrode 506 b of the switch transistor 506 is connectedto the pixel electrode 508. The source electrode 506 c of the switchtransistor 506 is connected to the video data line 504. A commonelectrode line 510 is used as the common electrode of the pixelelectrode 508. The common electrode line 510 is arranged in parallelwith the video data line 504. An “S”-type metal electrode 512 is builtaround the pixel region. The metal electrode 512 is controlled by thecommon electrode line 510. The common electrode line with the connectedmetal electrode line and the video data line are located on the samelayer.

FIG. 7B shows a cross-sectional view along line AA′ of FIG. 7A, in whichall of the liquid crystal molecule are in the splay state. A lowersubstrate 514 and an upper substrate 516 are opposite each other with aspecific distance therebetween. The lower substrate 514 and the uppersubstrate 516 are preferably made of a transparent insulator. A liquidcrystal layer 518 having a plurality of liquid crystal molecules issandwiched between the lower substrate 514 and the upper substrate 516,in which the plurality of liquid crystal molecules is in the splaystate. The video data line 504 and the metal line 512 are formed overthe lower substrate 514 and located on the same layer but isolated fromeach other. A pixel electrode 508 is formed on the inner surface of thelower substrate 514. Another isolation layer 532 is located between thevideo data line 504, the metal line 512 and the pixel electrode 508. Aconductor electrode 520 is formed on an inner surface of the uppersubstrate 516. Both the pixel electrode 508 and the conductor electrode520 are formed from a transparent conductor, and preferably, forexample, an ITO or IZO material.

The structure of the common electrode line with the connected metal lineand the video data line are located on the same layer can be applied inthe foregoing four embodiments.

In accordance with the foregoing description, an additional metalelectrode is built in the pixel region. The metal electrode iscontrolled by the common electrode. The liquid crystal molecules in thewhole pixel region are in the splay state. During operation, a voltageis first applied to the metal electrode to transform the liquid crystalmolecule over the metal electrode from the splay state into the bendstate. Then, a voltage is applied to the pixel electrode to make thewhole pixel region exhibit the bend state.

It is noted that the metal electrode can be positioned in the center ofthe pixel electrode or around the pixel electrode. The metal electrodeand the common electrode can be in the shape of a cross or in the shapeof an “H”. In accordance with the present invention, a complicatedmanufacturing process is avoided because the present invention does notrequire two orientation states in a liquid crystal cell. Moreover, agiven period for transforming the liquid crystal molecule from the splaystate into the bend state at the start of LCDs operation is notnecessary. Therefore, the LCDs using the pixel structure of the presentinvention has a high speed response as well as a high display quality.

On the other hand, the present invention also provides a drive circuitfor driving the metal electrode. FIG. 8A shows a waveform from negativeto positive of drive timing in accordance with the first embodiment. Thewaveform can be used in the foregoing four embodiments. According toFIGS. 3A to 3C and FIG. 8A, a voltage signal 404 is first applied to thecommon electrode 510. Therefore, the metal electrode 512 controlled bythe common electrode is also applied by this voltage signal 404. At thistime, the liquid crystal molecule located over the metal electrode 512is transformed from the splay state into the bend state. On the otherhand, part of the metal electrode 512 overlaps with the pixel electrodes508 a and 508 b and a voltage exists in the metal electrode 512, asshown in FIGS. 3B and 3C. All the metal electrode and pixel electrodes508 a and 508 b are conductors. Therefore, the overlapping parts 524 and526 can function as capacitors. In other words, this voltage applied tothe metal electrode 512 charges these overlapping parts 524 and 526 toraise the electrical potential of the pixel electrode.

At time T₁, by scanning the scan lines 502 and in accordance with thescan signals 402, the switch transistor 506 in a given scan line 502 isturned on. At the same time, pixel electrical potential 406 in the videodata line 504 is transferred to the pixel electrode 508 through theswitch transistor 506. In other words, a voltage difference is createdbetween the pixel electrode 508 and the conductor electrode 520 in theupper substrate 516 to transform the liquid crystal molecule from thesplay state into the bend state. It is noted that because theoverlapping parts 524 and 526 function as a capacitor, an initialelectric potention exists in the pixel electrode 508. In other words, itis easier to create a voltage in the pixel electrode 508 fortransforming the liquid crystal molecule from the splay state into thebend state. Therefore, the response velocity can be raised.

FIG. 8B shows a waveform from positive to negative of drive timing. Thewaveform may be used in the foregoing four embodiments. According toFIGS. 3A to 3C and FIG. 8B, a voltage signal 408 applied to the commonelectrode 510 is first switched from a high voltage to a low voltage.Therefore, the metal electrode 512 controlled by the common electrode isalso in a low voltage state. On the other hand, part of the metalelectrode 512 overlaps with the pixel electrodes 508 a and 508 b asshown in FIGS. 3B and 3C. All of the metal electrode, pixel electrodes508 a and 508 b are conductors. Therefore, the overlapping parts 524 and526 function as a capacitor. Therefore, when the metal electrode 512 isin a low electrical potential, the electrical potential 410 of the pixelelectrodes 508 a and 508 b is also reduced to a specific value at timeT₂. However, because the scan signal 412 does not select the switchtransistor 506 at this time, the switch transistor 506 is still turnedoff. In other words, the electrical potential 410 of the pixelelectrodes 508 a and 508 b is maintained at a fixed value. At time T₃,when the scan signal 412 in the scan line 502 selects the switchtransistor 506, the switch transistor 506 is turned on. The potential ofthe pixel electrodes 508 a and 508 b is discharged through the switchtransistor 506 to reduce the electrical potential 410.

FIG. 9A and FIG. 9B are the waveforms in accordance with the secondembodiment, of which FIG. 9A shows a waveform from positive to negativeof drive timing. The waveform may be used in the foregoing fourembodiments. According to FIGS. 3A to 3C and FIG. 9A, by scanning thescan lines 502 and in accordance with the scan signals 602, the switchtransistor 506 in a given scan line 502 is turned on. At the same time,pixel electrical potential 606 in the video data line 504 is transferredto the pixel electrode 508 through the switch transistor 506. Next, attime T₁, a voltage signal 604 is transformed from a low electricalpotential to a high electrical potential. In other words, the commonelectrode is also in a high electrical potential. Therefore, the metalelectrode 512 controlled by the common electrode 510 is also in a highelectrical potential that transforms the liquid crystal molecule fromthe splay state into the bend state.

On the other hand, part of the metal electrode 512 overlaps with thepixel electrodes 508 a and 508 b and a voltage exists in the metalelectrode 512, as shown in FIGS. 3B and 3C. All of the metal electrodeand pixel electrodes 508 a and 508 b are conductors. Therefore, theoverlapping parts 524 and 526 function as a capacitor. In other words,this voltage applied to the metal electrode 512 charges theseoverlapping parts 524 and 526 to raise the electrical potential 606 ofthe pixel electrode. It is easier to create a voltage in the pixelelectrode 508 for transforming the liquid crystal molecule from thesplay state into the bend state.

FIG. 9B shows the waveform from positive to negative of drive timing inaccordance with the second embodiment. The waveform may be used in theforegoing four embodiments. According to FIGS. 3A to 3C and 9B, byscanning the scan lines 502 and in accordance with the scan signals 612,the switch transistor 506 in a given scan line 502 is turned on toreduce the pixel electrical potential 610. On the other hand, part ofthe metal electrode 512 overlaps with the pixel electrodes 508 a and 508b as shown in FIGS. 3B and 3C. The overlapping parts 524 and 526function as a capacitor. This capacitor function maintain the pixelelectrical potential of the pixel electrode 508 at a fixed value. Attime T₂, the voltage signal 608 in the common electrode 510 istransferred from a high electrical potential to a low electricalpotential. The metal electrode 512 controlled by the common electrode510 is also at a low electrical potential, which discharges the chargestored in the overlapping parts 524 and 526 to reduce the pixelelectrical potential 610 of the pixel electrode 508.

FIG. 10A and FIG. 10B are the waveforms in accordance with the thirdembodiment, in which FIG. 10A shows a waveform from positive to negativeof drive timing. The waveform may be used in the foregoing fourembodiments. According to FIGS. 3A to 3C and 9A, by scanning the scanlines 502 and in accordance with the scan signals 202, the switchtransistor 506 in a given scan line 502 is turned on at time T₁. Next,pixel electrical potential 206 in the video data line 504 is transferredto the pixel electrode 508 through the switch transistor 506. At thesame time, a voltage signal 204 is transformed from a low electricalpotential into a high electrical potential. In other words, the commonelectrode is also at a high electrical potential. Therefore, the metalelectrode 512 controlled by the common electrode 510 is also at a highelectrical potential to transform the liquid crystal molecule from thesplay state into the bend state.

On the other hand, part of the metal electrode 512 overlaps with thepixel electrodes 508 a and 508 b, as shown in FIGS. 3B and 3C. All themetal electrodes and pixel electrodes 508 a and 508 b are conductors.The overlapping parts 524 and 526 function as a capacitor. Therefore,this voltage applied to the metal electrode 512 charges theseoverlapping parts 524 and 526 to raise the electrical potential 206 ofthe pixel electrode. It is easier to build a voltage in the pixelelectrode 508 for transforming the liquid crystal molecule from thesplay state into the bend state.

FIG. 10B shows a waveform from positive to negative of drive timing inaccordance with the third embodiment. The waveform may be used in theforegoing four pixel structure embodiments. According to FIGS. 3A to 3Cand 8B, by scanning the scan lines 502 and in accordance with the scansignals 212, the switch transistor 506 in a given scan line 502 isturned on to reduce the pixel electrical potential 210 at time T₂. Atthis time, the voltage signal 208 in the common electrode 510 istransformed from a high electrical potential in to a low electricalpotential. The metal electrode 512 controlled by the common electrode510 is also at a low electrical potential. On the other hand, part ofthe metal electrode 512 overlaps with the pixel electrodes 508 a and 508b as shown in FIGS. 3B and 3C. The overlapping parts 524 and 526function as a capacitor. Because the electrical potential in the commonelectrode 510 is at a low electrical potential, the charge stored in theoverlapping parts 524 and 526 is discharged to reduce the pixelelectrical potential 210 of the pixel electrode 508.

In accordance with the pixel structure of the present invention, part ofthe metal electrode overlaps with the pixel electrodes to function as acapacitor, which raises the response velocity.

FIG. 11 shows a top view of using the pixel electrode structure of thepresent invention in a TFT-LCD, in which the foregoing four pixelstructures may be used in the embodiment. The gate electrodes of theswitch transistors 14, 16, 18 and 19 are respectively connected to thescan lines 82, 84, 86 and 88. The drain electrodes of the switchtransistor 14, 16, 18 and 19 are respectively connected to the pixelelectrodes 24, 26, 28 and 19 and the source electrodes are respectivelyconnected to the video data line 72. The common lines 90, 92, 94 and 96are used as the common electrode of the pixel electrode 24, 26, 28 and19, respectively, to control the metal electrodes (not shown in figure).When the switch transistor 14 is selected by a given scan line, thevideo signals provided in the video data lines 72 are transferred to thepixel electrode 24 through the switch transistor 14 to show a picture inthe display.

FIG. 12A shows a drive circuit schematic diagram for generating awaveform as shown in FIGS. 8A and 8B for application to the pixelstructure as shown in FIG. 11. It is noted that FIG. 12A only depictsthe common electrode for driving two different pixel electrodes.However, this drive circuit may be extending for driving the whole pixelstructure. The drive method is same as is described in the following.

Referring to FIG. 11 and FIG. 12A, in accordance with the drive circuitof the present invention, the voltage signal in the output end V_(com1)is used to drive the common electrode 92 and the voltage signal in theoutput end V_(com2) is used to drive the common electrode 94. The switchof transistor 30 is controlled by the scan line 82 and the switch oftransistor 32 is controlled by the scan line 84. An inverter 34 islocated between the transistor 30 and the output end V_(com1) to invertthe input signal from the transistor 30. Another inverter 36 is locatedbetween the transistor 32 and the output end V_(com2) to invert thesignal in the output end V_(com1).

During operation, a frame signal V_(in) composed of two fields 38 and 40is input from the transistor 30, in which the time of each field is 1/60second. When the transistor 30 is turned on by the scan line 82, thefirst field signal 38 is transferred to the inverter 34 through thetransistor 30. The inverter 34 inverts the first field signal 38 andsends out the inverted first field signal 38 from the output endV_(com1) to drive the common electrode 92. Next, when the scan line 84turns on the transistor 32, the inverted first field signal 38 istransferred to the inverter 36 through the transistor 32. The inverter36 inverts the received signal again and sends out the same from theoutput end V_(com2) to drive the common electrode 94.

Therefore, in accordance with the waveform generated by the drivecircuit of the present invention, the switch transistor 16 of the pixelelectrode 26 is turned on by the scan signal in the scan line 84 afterthe common electrode 92 is driven by the drive signal from the outputend V_(com1). Therefore, the waveform shown in FIG. 7A is formed, inwhich the waveform 404 is the signal in the output end V_(com1) and thewaveform 402 is the signal in the scan line 84.

Next, when the transistor 30 receives the signal in the scan line 82again, the second field signal 40 is transferred to the inverter 34through the transistor 30. The inverter 34 may invert the second fieldsignal 40 and sends out the inverted second field signal 40 from theoutput end V_(com1) to drive the common electrode 92. Next, when thescan line 84 turns on the transistor 32, the inverted second fieldsignal 40 is transferred to the inverter 36 through the transistor 32.The inverter 36 inverts the received signal again and sends out the samefrom the output end V_(com2) to drive the common electrode 94.

Therefore, the switch transistor 16 of the pixel electrode 26 is turnedon by the scan signal in the scan line 84 after the common electrode 92receives the signal from the output end V_(com1). The waveform shown inFIG. 8B is thus formed, in which the waveform 408 is the signal in theoutput end V_(com1) and the waveform 412 is the signal in the scan line84.

FIG. 12B shows a detailed diagram of the drive circuit in FIG. 12A forgenerating a drive voltage. The operation method of the inverter isdescribed in the following. When the transistor 30 is turned on by thesignal in the scan line 82, the first field signal 38 is transferred tothe gate electrodes of the transistors 42 and 44 through the transistor30. The transistors 42 and 44 are still turned off because the firstfield signal 38 is at a low electrical potential. The transistor isturned on because the drain electrode and the source electrode areconnected together. The transistor is also turned on by the high voltagethrough the transistor 46. Therefore, the signal in the output endV_(com1) is a high voltage signal.

Similarly, when the signal in the scan line 82 turns the transistor 30on again, the second field signal 40 is transferred to the gateelectrodes of the transistors 42 and 44 through the transistor 30. Thetransistors 42 and 44 are turned on because the second field signal 40is at a high electrical potential. The gate electrode of the transistor48 are connected to the low electrical potential through the transistor42. Therefore, the transistor 48 is turned off. Therefore, the outputend V_(com1) is connected to a low voltage signal through the transistor44.

The drive circuit shown in FIG. 12A also can be used to generate awaveform as shown in FIGS. 9A and 9B. Referring to FIG. 11 and FIG. 12Atogether, the voltage signal in the output end V_(com1) is used to drivethe common electrode 92 and the voltage signal in the output endV_(com2) is used to drive the common electrode 94. However, the switchof the transistor 30 is controlled by the scan line 86 and the switch ofthe transistor 32 is controlled by the scan line 88. An inverter 34 islocated between the transistor 30 and the output end V_(com1) to invertthe input signal from the transistor 30. Another inverter 36 is locatedbetween the transistor 32 and the output end V_(com2) to invert thesignal in the output end V_(com1).

During operation, a frame signal V_(in) composed of two fields 38 and 40is input from the transistor 30, where the time of each field is 1/60seconds. When the transistor 30 is turned on by the scan signal in thescan line 86, the first field signal 38 is transferred to the inverter34 through the transistor 30. The inverter 34 inverts the first fieldsignal 38 and sends out the inverted first field signal 38 from theoutput end V_(com1) to drive the common electrode 92. Next, when thescan line 88 turns on the transistor 32, the inverted first field signal38 is transferred to the inverter 36 through the transistor 32. Theinverter 36 inverts the received signal again and sends out the samefrom the output end V_(com2) to drive the common electrode 94.

Therefore, in accordance with the waveform generated by the drivecircuit of the present invention, the common electrode 92 is driven bythe drive signal from the output end V_(com1) after the switchtransistor 18 of the pixel electrode 28 is turned on by the scan signalin the scan line 86. Therefore, the waveform shown in FIG. 8A is formed,in which the waveform 604 is the signal in the output end V_(com2) andthe waveform 602 is the signal in the scan line 86.

Next, when the transistor 30 receives the signal in the scan line 86again, the second field signal 40 is transferred to the inverter 34through the transistor 30. The inverter 34 inverts the second fieldsignal 40 and sends out the inverted second field signal 40 from theoutput end V_(com1) to drive the common electrode 92. Next, when thescan line 88 turns on the transistor 32, the inverted second fieldsignal 40 is transferred to the inverter 36 through the transistor 32.The inverter 36 inverts the received signal again and sends out the samefrom the output end V_(com2) to drive the common electrode 94.

Therefore, the common electrode 94 receives the signal from the outputend V_(com2) after the switch transistor 18 of the pixel electrode 28 isturned on by the scan signal in the scan line 86. The waveform shown inFIG. 8B is thus formed, in which the waveform 608 is the signal in theoutput end V_(com2) and the waveform 612 is the signal in the scan line86.

The drive circuit showing in FIG. 12A also can be used to generate awaveform as shown in FIGS. 10A and 10B. Referring to FIG. 11 and FIG.12A together, the voltage signal in the output end V_(com1) is used todrive the common electrode 92 and the voltage signal in the output endV_(com2) is used to drive the common electrode 94. However, the switchof the transistor 30 is controlled by the scan line 84 and the switch ofthe transistor 32 is controlled by the scan line 86. An inverter 34 islocated between the transistor 30 and the output end V_(com1) to invertthe input signal from the transistor 30. Another inverter 36 is locatedbetween the transistor 32 and the output end V_(com2) to invert thesignal in the output end V_(com1).

During operation, a frame signal V_(in) composed of two fields 38 and 40is input from the transistor 30, in which the time of each field is 1/60second. When the transistor 30 is turned on by the scan signal in thescan line 84, the first field signal 38 is transferred to the inverter34 through the transistor 30. The inverter 34 inverts the first fieldsignal 38 and sends out the inverted first field signal 38 from theoutput end V_(com1) to drive the common electrode 92. Next, when thescan line 86 turns on the transistor 32, the inverted first field signal38 is transferred to the inverter 36 through the transistor 32. Theinverter 36 inverts the received signal again and sends out the samefrom the output end V_(com2) to drive the common electrode 94.

Therefore, in accordance with the waveform generated by the drivecircuit of the present invention, the switch transistor 16 of the pixelelectrode 26 is turned on by the scan signal in the scan line 84. At thesame time, the common electrode 92 is driven by the drive signal fromthe output end V_(com1). The waveform shown in FIG. 9A is thus formed,in which the waveform 204 is the signal in the output end V_(com1) andthe waveform 202 is the signal in the scan line 84.

Next, when the transistor 30 receives the signal in the scan line 84again, the second field signal 40 is transferred to the inverter 34through the transistor 30. The inverter 34 inverts the second fieldsignal 40 and sends out the inverted second field signal 40 from theoutput end V_(com1) to drive the common electrode 92. Next, when thescan line 86 turns on the transistor 32, the inverted second fieldsignal 40 is transferred to the inverter 36 through the transistor 32.The inverter 36 inverts the received signal again and sends out the samefrom the output end V_(com2) to drive the common electrode 94.

Therefore, the switch transistor 16 of the pixel electrode 26 is turnedon by the scan signal in the scan line 84. At the same time, the commonelectrode 92 receives the signal from the output end V_(com1). Thewaveform shown in FIG. 9B is thus formed, in which the waveform 208 isthe signal in the output end V_(com2) and the waveform 212 is the signalin the scan line 84.

On the other hand, the liquid crystal molecules filling the pixel regionneed be aligned. The alignment arranges the orientation of the liquidcrystal molecules before a field is applied to the liquid crystaldisplay to sure all the liquid crystal molecule is arranged in the samedirection. A rubbing method is used to arrange the orientation. Anorientation line is generated on the orientation layer during therubbing process. These liquid crystal molecules are oriented along theselines.

In accordance with the present invention, a metal electrode is built inthe pixel region. The metal electrode is controlled by the commonelectrode. The liquid crystal molecules in the entire pixel region arein the splay state. A voltage is first applied to the metal electrode totransform the liquid crystal molecule over the metal electrode from thesplay state into the bend state during operation. Then, a voltage isapplied to the pixel electrode. In other words, liquid crystal moleculeslocated over the metal electrode are first transformed. However, whenthe voltage is applied to the common electrode, an unwanted crosswisefield is also generated around the common electrode. This crosswiseelectrical field affects the transformation of the liquid crystalmolecules located around the electrode. Therefore, the present inventionprovides an alignment method to reduce the effect the crosswiseelectrical field.

FIG. 13A illustrates a schematic diagram of the liquid crystal moleculesaligned in the direction perpendicular to the metal electrode. Theliquid crystal molecules 746 located over the metal electrode 742 andthe pixel electrode 744 are aligned in the direction as indicated by thearrow 740 perpendicular to the metal electrode 742. In FIG. 5A, themetal electrode 812 is built around the pixel electrode. Therefore,according to the alignment method illustrated in FIG. 13A, the liquidcrystal molecules 818 located over the metal electrode 812 and the pixelelectrode are aligned in the direction perpendicular to the metalelectrode 812.

FIG. 13B illustrates a schematic diagram of the liquid crystal moleculesaffected by a crosswise electrical field. When a voltage is applied to apixel electrode 744, a crosswise electrical field 750 is generated, thedirection of which is the reverse of the direction of the electricalfield 748 used to transform the liquid crystal molecules 746. In otherwords, a larger voltage must be applied to the pixel electrode 744 toovercome the crosswise electrical field so as to finish thetransformation of the liquid crystal molecules 746. Such a largervoltage requirement consumes power and time to finish the transformationof the liquid crystal molecules.

In FIG. 14A, illustrates a schematic diagram of the liquid crystalmolecules that is aligned in the direction parallel to the metalelectrode. The liquid crystal molecules 746 located over the metalelectrode 742 and the pixel electrode 744 are aligned in the directionas indicated by the arrow 752 that is parallel to the metal electrode742. In FIG. 5A, the metal electrode 812 is built around the pixelelectrode. Therefore, according to the alignment method as shown in FIG.14A, the liquid crystal molecules 818 located over the metal electrode812 and the pixel electrode are aligned in the direction parallel to themetal electrode 812.

FIG. 14B illustrates a schematic diagram of the transformation of theliquid crystal molecules when a voltage is applied to a pixel electrode744. The alignment direction of the liquid crystal molecules 746 isparallel to the arrangement direction of the metal electrode 742 in FIG.14A. Therefore, the crosswise electrical field generated by the metalelectrode 742 does not obstruct the liquid crystal moleculestransformation. In other words, it is not necessary to apply a largervoltage to the pixel electrode 744 to overcome the obstruction of thecrosswise electrical field.

Accordingly, the alignment direction of the liquid crystal molecules inthe foregoing embodiments is parallel to the arranged direction of themetal electrode. However, the arranged direction of the metal electrodeis not always in the same direction in a pixel region in theembodiments, which causes disorder in the liquid crystal moleculealignment direction in a pixel region. For solving this problem, Themetal electrode is designed and additional holes passing through thepixel electrode are formed in positions corresponding to the metalelectrode or common electrode so as to reduce the effect of thecrosswise electrical field and improve the transmission efficiency. Thefollowing eight embodiments illustrate the pixel structure appearancechange of the FIG. 4A to cooperate with the alignment direction of theliquid crystal molecules.

FIG. 15A illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe first embodiment of the present invention. The silicon island 706 aof the switch transistor 706 is connected to the scan line 702. When theswitch transistor 706 is selected, the scan signal in the scan line 702turns on the switch transistor 706. The video signal in the video dataline 704 is transferred to the pixel electrode 708 through the switchtransistor 706. The drain electrode 706 b of the switch transistor 706is connected to the pixel electrode 708. The source electrode 706 c ofthe switch transistor 706 is connected to the video data line 704. Acommon electrode line 710 is used as the common electrode of the pixelelectrode 708. A metal electrode 756 is built around the pixel region.The metal electrode 756 is controlled by the common electrode line 710.When operating the liquid crystal display, a voltage is applied to thecommon electrode and the metal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 756, aplurality of additional holes 758 passing through the pixel electrode708 is formed in positions corresponding to the common electrode line710. The hole 758 is an ellipse, a rectangle or another shape with amajor axis. It is noted that the direction of the major axis is parallelto the alignment direction of the liquid crystal molecules as indicatedby the arrow 754. On the other hand, the metal electrode 756 adjacent tothe scan line 702 is sawtoothed so that this metal electrode 756 has amajor axis in the direction indicated by an arrow 754. In other words,the liquid crystal molecules located over the metal electrode 756adjacent to the scan lines 702 can be aligned in the direction indicatedby an arrow 754.

FIG. 17A is an enlarged schematic diagram of the region 760 in FIG. 15A.A plurality of holes 758 passing through the pixel electrode 708 isformed in positions corresponding to the common electrode line 710.According to the preferred embodiment, the hole 758 is ellipsoidal. Theliquid crystal molecules 718 located over the pixel electrode arealigned in the direction parallel to the major axis of the hole 758, asindicated by the arrow 754. Holes 758 are separated from each other.Therefore, each hole 758 is treated as an independent electrode and hasa major axis, which cause a major crosswise electrical field, in thedirection indicated by the arrow 754. Therefore, the liquid crystalmolecules 718 is aligned in the direction parallel to the major axis ofthe hole 758 to reduce the effect of the crosswise electrical field, asshown in FIG. 17A. FIG. 17B illustrates a schematic diagram of theliquid crystal molecules when a voltage is applied to the commonelectrode.

FIG. 18A is an enlarged schematic diagram of the region 762 in FIG. 15A.The metal electrode 756 is sawtoothed. In this region 762, the metalelectrode 756 is composed of a base body 756 a and a plurality ofextending parts 756 b. Partial extending parts 756 b protrude from thepixel electrode 708. In other words, the metal electrode 756 has a majoraxis, which cause a major crosswise electrical field, in the directionindicated by the arrow 754. Therefore, the liquid crystal molecules 718is aligned in the direction parallel to the major axis, the extendingparts 756 b, to reduce the effect of the crosswise electrical field, asshown in FIG. 18A. FIG. 18B illustrates a schematic diagram of theliquid crystal molecules when a voltage is applied to the commonelectrode.

On the other hand, the region 764 and the region 762 both have the samestructure of the metal electrode 756 in FIG. 15A.

FIG. 15B illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe second embodiment of the present invention. The silicon island 706 aof the switch transistor 706 is connected to the scan line 702. When theswitch transistor 706 is selected, the scan signal in the scan line 702turns on the switch transistor 706. The video signal in the video dataline 704 is transferred to the pixel electrode 708 through the switchtransistor 706. The drain electrode 706 b of the switch transistor 706is connected to the pixel electrode 708. The source electrode 706 c ofthe switch transistor 706 is connected to the video data line 704. Acommon electrode line 710 is used as the common electrode of the pixelelectrode 708. A metal electrode 770 is built around the pixel region.The metal electrode 770 is controlled by the common electrode line 710.When operating the liquid crystal display, a voltage is applied to thecommon electrode and the metal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 770, the metalelectrode 770 adjacent to the video data line 704 is sawtoothed so thatmetal electrode 770 has a major axis in the direction indicated by anarrow 766. In other words, the liquid crystal molecules can be alignedin the direction indicated by an arrow 766. On the other hand, the pixelelectrode 708 in a pixel region is partially separated into two parts soas to expose the positions corresponding to the common electrode line710. The main purpose is to align the liquid crystal molecules in thedirection indicated by the arrow 766.

FIG. 19A is an enlarged schematic diagram of the region 768 in FIG. 15B.A trench passing through the pixel electrode 708 is formed in theposition corresponding to the common electrode line 710 to separate thepixel electrode into two parts. According to the preferred embodiment,the trench is a rectangular that has a major axis, which cause a majorcrosswise electrical field, in the direction indicated by the arrow 766.Therefore, the liquid crystal molecules 718 located over the pixelelectrode 708 are aligned in a direction, indicated by the arrow 766,parallel to the common electrode line 710 to reduce the effect of thecrosswise electrical field. FIG. 19B illustrates a schematic diagram ofthe liquid crystal molecules when a voltage is applied to the commonelectrode.

On the other hand, the metal electrode 770 adjacent to the video dataline 704 is sawtoothed, whose diagram is similar to FIG. 18A. The metalelectrode 770 has a plurality of extending parts outside the pixelelectrode 708. These extending parts cause a major crosswise electricalfield in the direction indicated by the arrow 766. Therefore, the liquidcrystal molecules 718 are aligned in the direction indicated by thearrow 766.

FIG. 15C illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe third embodiment of the present invention. The silicon island 706 aof the switch transistor 706 is connected to the scan line 702. When theswitch transistor 706 is selected, the scan signal in the scan line 702turns on the switch transistor 706. The video signal in the video dataline 704 is transferred to the pixel electrode 708 through the switchtransistor 706. The drain electrode 706 b of the switch transistor 706is connected to the pixel electrode 708. The source electrode 706 c ofthe switch transistor 706 is connected to the video data line 704. Acommon electrode line 710 is used as the common electrode of the pixelelectrode 708. A metal electrode 772 is built around the pixel region.The metal electrode 772 is controlled by the common electrode line 710.When operating the liquid crystal display, a voltage is applied to thecommon electrode and the metal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 772, aplurality of additional holes 758 passing through the pixel electrode708 is formed in the positions corresponding to the common electrodeline 710. On the other hand, a plurality of additional holes 782 passingthrough the pixel electrode 708 is formed in the positions correspondingto the metal electrode 772 adjacent to the scan lines 702. The holes 758are ellipses, rectangles or any other shape with a major axis. It isnoted that the direction of the major axis is parallel to the alignmentdirection of the liquid crystal molecules as indicated by the arrow 754.On the other hand, the metal electrode 772 adjacent to video data line704 is out of the pixel electrode 708. The alignment direction of theliquid crystal molecules according to the preferred embodiment isparallel to the direction indicated by the arrow 754.

FIG. 20A is an enlarged schematic diagram of the region 784 in FIG. 15C.The metal electrode 772 adjacent to the video data line is out of thepixel electrode 708. According to the preferred embodiment, the metalelectrode 772 out of the pixel electrode 708 has a major axis, whichcause a major crosswise electrical field, in the direction indicated bythe arrow 754. Therefore, the liquid crystal molecules 718 located overthe pixel electrode 708 are aligned in the direction, as indicated bythe arrow 754, parallel to the metal electrode 772 to reduce the effectof the crosswise electrical field. FIG. 20B illustrates a schematicdiagram of the liquid crystal molecules when a voltage is applied to thecommon electrode.

On the other hand, a plurality of holes 758 passing through the pixelelectrode 708 is formed on the positions corresponding to the metalelectrode 772 adjacent to the scan lines 702, whose diagram is similarto FIG. 17A. According to the preferred embodiment, the holes 758 arerectangular in shape. However, any other shape with a major axis alsocan be used in the preferred embodiment. The liquid crystal molecules718 located over the pixel electrode 708 are aligned in the directionparallel to the major axis of the holes 758, as indicated by the arrow754.

FIG. 15D illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe fourth embodiment of the present invention. The silicon island 706 aof the switch transistor 706 is connected to the scan line 702. When theswitch transistor 706 is selected, the scan signal in the scan line 702turns on the switch transistor 706. The video signal in the video dataline 704 is transferred to the pixel electrode 708 through the switchtransistor 706. The drain electrode 706 b of the switch transistor 706is connected to the pixel electrode 708. The source electrode 706 c ofthe switch transistor 706 is connected to the video data line 704. Acommon electrode line 710 is used as the common electrode of the pixelelectrode 708. A metal electrode 774 is built around the pixel region.The metal electrode 774 is controlled by the common electrode line 710.When operating the liquid crystal display, a voltage is applied to thecommon electrode and the metal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 774, aplurality of additional holes 786 passing through the pixel electrode708 is formed in the positions corresponding to the metal electrode 774adjacent to the video data lines 704. The holes 786 are ellipses,rectangles or any other shape with a major axis. It is noted that thedirection of the major axis is parallel to the alignment direction ofthe liquid crystal molecules as indicated by the arrow 766. On the otherhand, the metal electrode 774 adjacent to scan lines 702 is out of thepixel electrode 708. A trench passing through the pixel electrode 708 isformed in the position corresponding to the common electrode line 710.

The metal electrode 774 adjacent to the scan lines 702 is out of thepixel electrode 708. According to the preferred embodiment, the metalelectrode 774 out of the pixel electrode 708 has a major axis, whichcauses a major crosswise electrical field in the direction indicated bythe arrow 766. Therefore, the liquid crystal molecules located over thepixel electrode 708 are aligned in the direction, indicated by arrow766, parallel to the metal electrode 774 to reduce the effect of thecrosswise electrical field, whose diagram is similar to FIG. 20A.

On the other hand, a trench passing through the pixel electrode 708 isformed in the position corresponding to the common electrode line 710 toseparate the pixel electrode into two parts. According to the preferredembodiment, the trench is a rectangle with a major axis, which causes amajor crosswise electrical field, in the direction indicated by thearrow 766. Therefore, the liquid crystal molecules located over thepixel electrode 708 are aligned in the direction indicated by arrow 766.

Additionally, a plurality of holes 786 passing through the pixelelectrode 708 is formed in positions corresponding to the metalelectrode 774 adjacent to the video data lines 704, whose diagram issimilar to FIG. 17A. According to the preferred embodiment, the holes786 are rectangular in shape. However, any other shape with a major axisalso can be used in the preferred embodiment. The liquid crystalmolecules located over the pixel electrode 708 are aligned in thedirection parallel to the major axis of the holes 786, as indicated bythe arrow 766.

FIG. 15E illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe fifth embodiment of the present invention. The silicon island 706 aof the switch transistor 706 is connected to the scan line 702. When theswitch transistor 706 is selected, the scan signal in the scan line 702turns on the switch transistor 706. The video signal in the video dataline 704 is transferred to the pixel electrode 708 through the switchtransistor 706. The drain electrode 706 b of the switch transistor 706is connected to the pixel electrode 708. The source electrode 706 c ofthe switch transistor 706 is connected to the video data line 704. Acommon electrode line 710 is used as the common electrode of the pixelelectrode 708. A metal electrode 790 is built around the pixel region.The metal electrode 790 is controlled by the common electrode line 710.When operating the liquid crystal display, a voltage is applied to thecommon electrode and the metal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 790, aplurality of additional holes 758 passing through the pixel electrode708 is formed in positions corresponding to the common electrode line710. The hole 758 is an ellipse, a rectangle or any other shape with amajor axis. It is noted that the direction of the major axis is parallelto the alignment direction of the liquid crystal molecules, as indicatedby the arrow 754. On the other hand, the metal electrode 790 adjacent tothe scan line 702 is sawtoothed so that this metal electrode 790 has amajor axis in the direction indicated by an arrow 754. In other words,the liquid crystal molecules located over the metal electrode 790adjacent to the scan lines 702 can be aligned in the direction indicatedby an arrow 754. The main difference between the first embodiment andthe fifth embodiment is that additional holes 791 passing through thepixel electrode 708 are formed in positions corresponding to the metalelectrode 790 adjacent to the scan lines 702. The hole 791 is anellipse, a rectangle or any other shape with a major axis. It is notedthat the direction of the major axis is parallel to the alignmentdirection of the liquid crystal molecules as indicated by the arrow 754.

A plurality of holes 758 passing through the pixel electrode 708 isformed on the positions corresponding to the common electrode line 710.According to the preferred embodiment, hole 758 is rectangular in shape.The liquid crystal molecules located over the pixel electrode arealigned in the direction parallel to the major axis of the hole 758, asindicated by the arrow 754 in FIG. 17A. Each hole 758 has a major axis,which causes a major crosswise electrical field, in the directionindicated by the arrow 754. Therefore, the liquid crystal molecules arealigned in the direction parallel to the major axis of the hole 758 toreduce the effect of the crosswise electrical field.

The metal electrode 790 adjacent to the scan lines 702 is sawtoothed,whose diagram is similar to FIG. 18A. The metal electrode 790 has aplurality of extending parts 792 outside the pixel electrode 708. On theother hand, additional holes 791 passing through the pixel electrode 708are formed in the positions corresponding to the metal electrode 790 andadjacent to the scan lines 702. The hole 791 is an ellipse, a rectangleor any other shape with a major axis. The main purpose of forming theadditional holes 791 is to reduce the effect of the crosswise electricalfield generated by the scan lines 702.

FIG. 15F illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe sixth embodiment of the present invention. The silicon island 706 aof the switch transistor 706 is connected to the scan line 702. When theswitch transistor 706 is selected, the scan signal in the scan line 702turns on the switch transistor 706. The video signal in the video dataline 704 is transferred to the pixel electrode 708 through the switchtransistor 706. The drain electrode 706 b of the switch transistor 706is connected to the pixel electrode 708. The source electrode 706 c ofthe switch transistor 706 is connected to the video data line 704. Acommon electrode line 710 is used as the common electrode of the pixelelectrode 708. A metal electrode 792 is built around the pixel region.The metal electrode 792 is controlled by the common electrode line 710.When operating the liquid crystal display, a voltage is applied to thecommon electrode and the metal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 792, the metalelectrode 792 adjacent to the video data line 704 is sawtoothed so thatthis metal electrode 792 has a major axis in the direction indicated byan arrow 766. In other words, the liquid crystal molecules can bealigned in the direction indicated by an arrow 766. On the other hand,the pixel electrode 708 in a pixel region is partially separated intotwo parts so that the positions corresponding to the common electrodeline 710 are exposed. The main purpose is to align the liquid crystalmolecules in the direction indicated by the arrow 766. The maindifference between the second embodiment and the sixth embodiment isthat additional holes 793 passing through the pixel electrode 708 areformed in the positions corresponding to the metal electrode 792 andadjacent to the video data lines 704. The hole 793 is an ellipse, arectangle or any other shape with a major axis. It is noted that thedirection of the major axis is parallel to the alignment direction ofthe liquid crystal molecules as indicated by the arrow 766.

A trench passing through the pixel electrode 708 is formed in theposition corresponding to the common electrode line 710 to separate thepixel electrode into two parts, whose diagram is similar to FIG. 19A.According to the preferred embodiment, trench is a rectangle with amajor axis, which causes a major crosswise electrical field in thedirection indicated by the arrow 766. Therefore, the liquid crystalmolecules located over the pixel electrode 708 are aligned in thedirection indicated by the arrow 766.

On the other hand, metal electrode 792 adjacent to the video data line704 is sawtoothed, whose diagram is similar to FIG. 18A. The metalelectrode 792 has a plurality of extending parts 794 outside the pixelelectrode 708. These extending parts cause a major crosswise electricalfield in the direction indicated by the arrow 766. Therefore, the liquidcrystal molecules are aligned in the direction indicated by the arrow766. Additionally, additional holes 793 passing through the pixelelectrode 708 are formed in positions corresponding to the metalelectrode 792 and adjacent to the video data lines 704. The hole 793 isa rectangle according to the preferred embodiment. However, an ellipseor any other shape with a major axis also can be used in the presentinvention. The main purpose of forming the additional holes 793 is toreduce the effect of the crosswise electrical field generated by thevideo data lines 704. The liquid crystal molecules located over thepixel electrode 708 are aligned in the direction parallel to the majoraxis of the holes 793, as indicated by the arrow 766.

FIG. 15G illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe seventh embodiment of the present invention. The silicon island 706a of the switch transistor 706 is connected to the scan line 702. Whenthe switch transistor 706 is selected, the scan signal in the scan line702 turns on the switch transistor 706. The video signal in the videodata line 704 is transferred to the pixel electrode 708 through theswitch transistor 706. The drain electrode 706 b of the switchtransistor 706 is connected to the pixel electrode 708. The sourceelectrode 706 c of the switch transistor 706 is connected to the videodata line 704. A common electrode line 710 is used as the commonelectrode of the pixel electrode 708. A metal electrode 795 is builtaround the pixel region. The metal electrode 795 is controlled by thecommon electrode line 710. When operating the liquid crystal display, avoltage is applied to the common electrode and the metal electrode atthe same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 795, aplurality of holes 758 passing through the pixel electrode 708 is formedin the positions corresponding to the common electrode line 710.Additionally, holes 758 passing through the pixel electrode 708 are alsoformed in the positions corresponding to the metal electrode 795adjacent to the scan lines 702. The main difference between the thirdembodiment and the seventh embodiment is that additional holes 796 arerespectively formed between any two adjacent holes 758. The hole 758 or796 is an ellipse, a rectangle or any other shape with a major axis. Itis noted that the direction of the major axis is parallel to thealignment direction of the liquid crystal molecules as indicated by thearrow 754.

The metal electrode 795 adjacent to the video data line 704 is out ofthe pixel electrode 708, whose diagram is similar to FIG. 20A. Accordingto the preferred embodiment, the metal electrode 795 out of the pixelelectrode 708 has a major axis, which causes a major crosswiseelectrical field, in the direction indicated by the arrow 754.Therefore, the liquid crystal molecules located over the pixel electrode708 is aligned in the direction, indicated by arrow 754, parallel to themetal electrode 795 to reduce the effect of the crosswise electricalfield.

Additionally, a plurality of holes 758 passing through the pixelelectrode 708 is formed in the positions corresponding to the metalelectrode 795 adjacent to the scan line 702, whose diagram is similar toFIG. 17A. Additional holes 796 are respectively formed between any twoadjacent holes 758. The main purpose of forming the additional holes 796is to reduce the effect of the crosswise electrical field generated bythe scan lines 702. The liquid crystal molecules located over the pixelelectrode 708 are aligned in the direction parallel to the major axis ofthe holes 796, as indicated by the arrow 754.

FIG. 15H illustrates a schematic diagram of a pixel structure appearancechange of FIG. 4A cooperating with this alignment method according tothe eighth embodiment of the present invention. The silicon island 706 aof the switch transistor 706 is connected to the scan line 702. When theswitch transistor 706 is selected, the scan signal in the scan line 702turns on the switch transistor 706. The video signal in the video dataline 704 is transferred to the pixel electrode 708 through the switchtransistor 706. The drain electrode 706 b of the switch transistor 706is connected to the pixel electrode 708. The source electrode 706 c ofthe switch transistor 706 is connected to the video data line 704. Acommon electrode line 710 is used as the common electrode of the pixelelectrode 708. A metal electrode 797 is built around the pixel region.The metal electrode 797 is controlled by the common electrode line 710.When operating the liquid crystal display, a voltage is applied to thecommon electrode and the metal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 797, aplurality of holes 786 passing through the pixel electrode 708 is formedin the positions corresponding to the metal electrode 797 adjacent tothe video data lines 704. Additionally, additional holes 798 arerespectively formed between any two adjacent holes 786. The hole 786 or798 is an ellipse, a rectangle or any other shape with a major axis. Itis noted that the direction of the major axis is parallel to thealignment direction of the liquid crystal molecules as indicated by thearrow 766. On the other hand, the metal electrodes 797 adjacent to thescan lines 702 are out of the pixel electrode 708. Moreover, the pixelelectrode 708 in a pixel region is partially separated into two parts sothat the positions corresponding to the common electrode line 710 areexposed.

The metal electrode 797 adjacent to the scan lines 702 is out of thepixel electrode 708. According to the preferred embodiment, the metalelectrode 797 out of the pixel electrode 708 has a major axis, whichcauses a major crosswise electrical field, in the direction indicated bythe arrow 766. Therefore, the liquid crystal molecules located over thepixel electrode 708 are aligned in the direction, indicated by the arrow766, that is parallel to the metal electrode 797 to reduce the effect ofthe crosswise electrical field, whose diagram is similar to FIG. 20A.

On the other hand, a trench passing through the pixel electrode 708 isformed in the position corresponding to the common electrode line 710 toseparate the pixel electrode into two parts, as illustrated in FIG. 19A.According to the preferred embodiment, the trench is a rectangle thathas a major axis, which causes a major crosswise electrical field, inthe direction indicated by the arrow 766. Therefore, the liquid crystalmolecules located over the pixel electrode 708 are aligned in thedirection indicated by the arrow 766.

Additionally, holes 786 passing through the pixel electrode 708 areformed in the positions corresponding to the metal electrode 797 andadjacent to the video data lines 704 whose diagram is similar to FIG.17A. Additional holes 798 are respectively formed between any twoadjacent holes 786. The main purpose of forming the additional holes 798is to reduce the effect of the crosswise electrical field generated bythe scan lines video data lines 704. The liquid crystal moleculeslocated over the pixel electrode 708 is aligned in the directionparallel to the major axis of the holes 798, as indicated by the arrow766.

Accordingly, the method of changing the pixel structure appearance ofFIG. 4A described in the foregoing eight embodiments cooperating withthis alignment method to reduce the effect of the crosswise electricalfield also can be used in other types of pixel structure. For example,the following embodiment describes the method is used to change thepixel structure appearance of FIG. 5A.

FIG. 16A illustrates a schematic diagram of a pixel structure appearancechange of FIG. 5A cooperating with this alignment method according tothe ninth embodiment of the present invention. The silicon island 806 aof the switch transistor 806 is connected to the scan line 802. Thedrain electrode 806 b of the switch transistor 806 is connected to thepixel electrode 808. The source electrode 806 c of the switch transistor806 is connected to the video data line 804. A common electrode line 810is used as the common electrode of the pixel electrode 808. A “H” typepixel structure composed of the metal electrode 856 and the commonelectrode 810 is formed in the pixel region. The metal electrode 856 iscontrolled by the common electrode line 810. When operating the liquidcrystal display, a voltage is applied to the common electrode and themetal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 856, aplurality of additional holes 858 passing through the pixel electrode808 is formed in the positions corresponding to the common electrodeline 810. The hole 858 is an ellipse, a rectangle or any other shapewith a major axis. It is noted that the direction of the major axis isparallel to the alignment direction of the liquid crystal molecules asindicated by the arrow 854. On the other hand, the metal electrode 856adjacent to the video data line 804 is out of the pixel electrode 808.Therefore, the liquid crystal molecules located over the metal electrode856 adjacent to the video data lines 804 can be aligned in the directionindicated by an arrow 854.

The metal electrode 856 adjacent to the video data line 804 is out ofthe pixel electrode 808, whose diagram is similar to FIG. 20A. Accordingto the preferred embodiment, the metal electrode 856 out of the pixelelectrode 808 has a major axis, which causes a major crosswiseelectrical field in the direction indicated by the arrow 854. Therefore,the liquid crystal molecules located over the pixel electrode 808 isaligned in the direction, indicated by the arrow 854, that is parallelto the metal electrode 856 to reduce the effect of the crosswiseelectrical field.

On the other hand, a plurality of holes 858 passing through the pixelelectrode 808 is formed in the positions corresponding to the commonelectrode line 810, whose diagram is similar to FIG. 17A. According tothe preferred embodiment, the hole 858 is a rectangle. However, anellipse or any other shape with a major axis also can be used in thepreferred embodiment. The liquid crystal molecules located over thepixel electrode are aligned in the direction parallel to the major axisof the hole 858, as indicated by the arrow 854.

FIG. 16B illustrates a schematic diagram of a pixel structure appearancechange of FIG. 5A cooperating with this alignment method according tothe tenth embodiment of the present invention. The silicon island 806 aof the switch transistor 806 is connected to the scan line 802. Thedrain electrode 806 b of the switch transistor 806 is connected to thepixel electrode 808. The source electrode 806 c of the switch transistor806 is connected to the video data line 804. A common electrode line 810is used as the common electrode of the pixel electrode 808. A “H” typepixel structure composed of the metal electrode 870 and the commonelectrode 810 is formed in the pixel region. The metal electrode 870 iscontrolled by the common electrode line 810. When operating the liquidcrystal display, a voltage is applied to the common electrode and themetal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 870, the metalelectrode 870 adjacent to the video data line 804 is sawtoothed so thatthis metal electrode 870 has a major axis in the direction indicated byan arrow 866. In other words, the liquid crystal molecules can bealigned in the direction indicated by an arrow 866. On the other hand,the pixel electrode 808 in a pixel region is partially separated intotwo parts so that the positions corresponding to the common electrodeline 810 are exposed. The main purpose is to align the liquid crystalmolecules in the direction indicated by the arrow 866.

A trench passing through the pixel electrode 808 is formed in theposition corresponding to the common electrode line 810 to separate thepixel electrode into two parts, whose diagram is similar to FIG. 19A.According to the preferred embodiment, the trench is a rectangle with amajor axis, which causes a major crosswise electrical field in thedirection indicated by the arrow 866. Therefore, the liquid crystalmolecules located over the pixel electrode 808 are aligned in thedirection, indicated by the arrow 866, that is parallel to the commonelectrode line 810 to reduce the effect of the crosswise electricalfield.

On the other hand, the metal electrode 870 adjacent to the video dataline 804 is sawtoothed, whose diagram is similar to FIG. 18A. The metalelectrode 870 has a plurality of extending parts out of the pixelelectrode 808. These extending parts cause a major crosswise electricalfield in the direction indicated by the arrow 866. Therefore, the liquidcrystal molecules are aligned in the direction indicated by the arrow866.

FIG. 16C illustrates a schematic diagram of a pixel structure appearancechange of FIG. 5A cooperating with this alignment method according tothe eleventh embodiment of the present invention. The silicon island 806a of the switch transistor 806 is connected to the scan line 802. Thedrain electrode 806 b of the switch transistor 806 is connected to thepixel electrode 808. The source electrode 806 c of the switch transistor806 is connected to the video data line 804. A common electrode line 810is used as the common electrode of the pixel electrode 808. A “H” typepixel structure composed of the metal electrode 878 and the commonelectrode 810 is formed in the pixel region. The metal electrode 878 iscontrolled by the common electrode line 810. When operating the liquidcrystal display, a voltage is applied to the common electrode and themetal electrode at the same time.

Cooperating with the alignment direction of the liquid crystal moleculesparallel to the arranged direction of the metal electrode 878, the metalelectrode 878 adjacent to video data line 804 is sawtoothed so that thismetal electrode 878 has a major axis in the direction indicated by anarrow 880. In other words, the liquid crystal molecules can be alignedin the direction indicated by an arrow 880. On the other hand, the pixelelectrode 808 in a pixel region is partially separated into two parts sothat the positions corresponding to the common electrode line 810 areexposed. The main purpose is to align the liquid crystal molecules inthe direction indicated by the arrow 880.

A trench passing through the pixel electrode 808 is formed in theposition corresponding to the common electrode line 810 to separate thepixel electrode into two parts, whose diagram is similar to FIG. 19A.According to the preferred embodiment, the liquid crystal moleculeslocated over the pixel electrode 808 are aligned in the direction,indicated by the arrow 866, that is parallel to the common electrodeline 810 to reduce the effect of the crosswise electrical field.

The metal electrode 878 adjacent to the video data line 804 issawtoothed, whose diagram is similar to FIG. 18A. The metal electrode878 has a plurality of extending parts 874 out of the pixel electrode808. Holes 876 are respectively formed in any two adjacent extendingparts 874 to reduce the effect of the crosswise electrical fieldgenerated by the video data line 804.

It is noted that although all of the embodiments are related to thestructure of the common electrode line with the connected metalelectrode line and the video data line located on different layers,these embodiments also can be used in the structure where the commonelectrode line with the connected metal electrode line and the videodata line are located on the same layer.

Accordingly, for reducing the crosswise electrical field effect duringliquid crystal molecules transformation, the alignment direction isparallel to the metal electrode in the present invention. On the otherhand, additional holes passing through the pixel electrode are formed inthe positions corresponding to the metal electrode or common electrodeso as to reduce the crosswise electrical field. The hole 858 is anellipse, a rectangle or any other shape with a major axis.

As is understood by a person skilled in the art, the foregoingdescriptions of the preferred embodiment of the present invention are anillustration of the present invention rather than a limitation thereof.Various modifications and similar arrangements are included within thespirit and scope of the appended claims. The scope of the claims shouldbe accorded to the broadest interpretation so as to encompass all suchmodifications and similar structures. While a preferred embodiment ofthe invention has been illustrated and described, it will be appreciatedthat various changes can be made therein without departing from thespirit and scope of the invention.

1. A liquid crystal display driving method, wherein said liquid crystaldisplay comprises a first substrate having a plurality of scan lines,video data lines and pixel regions disposed therein, a second substratehaving a conductor electrode disposed therein and a liquid crystal layersandwiched between said first substrate and said second substrate, eachpixel region comprising a switching transistor, a pixel electrodeconnected with said switch transistor, and a common electrode and ametal electrode extending from said common electrode, wherein said pixelelectrode, said common electrode and said metal electrode are isolatedfrom each other, said drive method comprising the steps: (a)transforming a voltage applied in said common electrode from a firstvoltage to a second voltage; (b) conducting said switching transistors,wherein video data is transferred from said video data lines to saidpixel regions; (c) closing said switching transistors to maintain saidvideo data in said pixel regions; (d) transforming the voltage appliedto said common electrode from said second voltage to said first voltage;(e) conducting said switching transistors, wherein said video data isreleased from said pixel regions; (f) closing said switchingtransistors; and (g) repeating (a) step to (f) step.
 2. The liquidcrystal display driving method of claim 1, wherein said (a) step and (b)step can be performed together, and when said (a) step and (b) step areperformed together, said (d) step and (e) step are also performedtogether.
 3. The liquid crystal display driving method of claim 1,wherein said second voltage is higher than said first voltage.
 4. Theliquid crystal display driving method of claim 1, wherein the gateelectrodes of said switching transistors are connected to said scanlines.
 5. The liquid crystal display driving method of claim 1, whereinsaid pixel electrodes are connected to said video data lines when saidswitching transistors are conducted.